Security system sirens and loudspeakers are critical elements in gathering and/or evacuating people during an incident, a fire, a natural or industrial disaster. Checking their working order on a regular basis is therefore required.
It is known to send direct current over the electrical connection that supplies a loudspeaker and to measure the resistance over this connection. Depending on the resistance measured, it can be determined whether the loudspeaker's coil is supplied by the connection and is in working order.
However, this technique has a number of drawbacks. Firstly, the continuous consumption of electrical power is not negligible. Secondly, permanently maintaining the loudspeaker membrane in an offset position in relation to its power-off balance position, causes this membrane to deteriorate, causes mechanical problems with the coil and encourages corrosion effects. In particular, the inventors have discovered that it is this continuous supply to the coil of some loudspeakers located outdoors that causes their soiling with dust, sand or salt.
This soiling causes:                matter to accumulate and        a crust to form on the loudspeaker's membrane.        
The result of these drawbacks, in particular, is that the loudspeaker ages and the sound power it emits for the same electrical control signal gradually decreases. Thus, the loss of efficiency of these loudspeakers is accelerated.